'''[http://grub.enbug.org/ GRUB2]''' is a modular, multiboot-capable bootloader for many operating systems that can be used as a payload for coreboot.

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'''[https://www.gnu.org/software/grub/grub.html GRUB2]''' is a modular, multiboot-capable bootloader for many operating systems that can be used as a payload for coreboot.

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== Status ==

== Status ==

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* A significant amount of work has been put into GRUB2 in our [[Monotone Repository|monotone repository]], which also provides snapshots.

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* The mainline version of GRUB2 has a [http://grub.enbug.org/CoreBoot wiki page on the coreboot port] (Update: no longer available)

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* The mainline version of GRUB2 has a [http://grub.enbug.org/CoreBoot wiki page on the coreboot port].

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* Additional information about our former GRUB2 effort (which was part of Google Summer of Code 2007) can be found in the history of this page. Don't expect any link there to work.

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* There is currently no work going on in our GRUB2 repository, not even synchronization to the upstream repository. If you require the additional features of our branch below, go ahead. Otherwise, upstream might serve you better. Or not.

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* As an alternative, you could consider using [[FILO]]. Both FILO and GRUB2 have various advantages and disadvantages. Which of the two is better suited depends on your requirements.

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* Yet another alternative is to not put GRUB into the BIOS ROM, but have it run from your disk as you would with a vendor BIOS. For that, you can use [[SeaBIOS]] as payload, which will then be able to run either GRUB1 or GRUB2 from your disk.

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== How to build GRUB2 as a payload ==

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It's recommended to use a recent snapshot of the '''allpatches''' branch in the [[Monotone Repository|GRUB2 monotone repository]]

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(you can also just download http://coreboot.org/viewmtn/branch/head/tar/org.coreboot.grub2.allpatches - which resolves to the latest revision on that branch; the top level directory in the resulting tarball represents the revision ID, which is a SHA-1 value over revision data, and thus varies wildly).

| in the .usb branch, provides an uhci driver and usb storage support. highly experimental at this time

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|}

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=== Building a diskimage ===

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If you are using coreboot v2, the firmware image is not a LAR archive, as in coreboot v3. If you want to place files in the coreboot+grub2 image, you can still create a diskimage and include it in your payload.

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# create a lar/cpio/tar file (cpio must be gnu cpio. files created by other cpios might not be compatible)

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# add <code>-m lar/cpio-file</code> to your grub-mkimage command line

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Per default GRUB2 looks for a configuration file [http://grub.enbug.org/grub.cfg grub.cfg] in the disk image. The path is

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(memdisk)/grub.cfg

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== Checking Signatures ==

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Currently the tools for crypto signature verification are not built automatically. To build them, run

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$ cd libs/sigtools

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$ make

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=== Using sigtools ===

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Create a key pair filename.pub and filename.sec with

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$ genkeypair filename

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Create a signature of candidate using keyfile.sec and save it as candidate.sig:

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$ gensig keyfile candidate

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=== Verification in GRUB2 ===

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Load /key.pub as public key and block access to all unsigned files with

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$ load-pubkey /key.pub

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Verify foo using the signature foo.sig, reporting success or failure and grant access to the file foo with:

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$ validate /foo /foo.sig

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Example:

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multiboot grub-invaders # fails

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validate grub-invaders grub-invaders.sig

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multiboot grub-invaders # this time it succeeds

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== Hints and Tricks ==

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=== Loading grub.cfg from disk ===

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It is suggested that grub.cfg is contained in a memdisk/lar image. This grub.cfg can be used to load other configuration files from any mass storage media. If you want to load a grub.cfg from the first device that contains one, your in-flash grub.cfg can look like this:

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search -f -s /grub.cfg

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configfile /grub.cfg

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== To Do ==

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* USB stack integration (in progress).

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* See more information in the "[http://tracker.coreboot.org/trac/coreboot/milestone/Port%20GRUB2%20to%20coreboot Porting GRUB2 to coreboot]" milestone in the coreboot issue tracker.

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== History ==

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[[User:PatrickGeorgi|Patrick Georgi]] has been working on GRUB2 for coreboot during the Google Summer of Code 2007. He made an [http://coreboot.org/~oxygene/lbgrub2-20070820-1.tar.bz2 original code submission] on August 20th 2007. If you care, there is [http://coreboot.org/~oxygene/lbgrub2-instructions.txt documentation on how to use it], but that work is based on a very old version of GRUB2.

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For various reasons, [[User:RobertMillan|Robert Millan]] of the GRUB project did another original implementation, which got merged, so we moved our effort to their new code base and continued from there.

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== Compiling GRUB2 for being use as a payload (WIP HOWTO) ==

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See [[Talk:GRUB2]] and [https://lists.gnu.org/archive/html/grub-devel/2011-06/msg00003.html here] for more details.

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Additional information about our former GRUB2 effort (which was part of Google Summer of Code 2007) can be found in the history of this page. Don't expect any link there to work.

As an alternative, you could consider using FILO. Both FILO and GRUB2 have various advantages and disadvantages. Which of the two is better suited depends on your requirements.

Yet another alternative is to not put GRUB into the BIOS ROM, but have it run from your disk as you would with a vendor BIOS. For that, you can use SeaBIOS as payload, which will then be able to run either GRUB1 or GRUB2 from your disk.